Control and dial mechanism for variable frequency oscillator



R. L. TUCKER CONTROL AND DIAL MECHANISM FOR VARIABLE FREQUENCY OSCILLATOR Filed July 27 1956 Robe/"f Z. Tucker IN VEN TOR.

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i atentecl July 1, 1958 CONTRGL AND DEAL MECHANISM FOR VAR FREQUENCY UCILLATOR Robert L. Tucker, Tulsa, Elllrla, assignor to Southwestern industrial Electronics Company, Harrrs County, Bah, a corporation of Delaware Application duly 27, 1956, Serial No. 6%,515

6 Claims. (Cl, 318--2) This invention relates to motor driven variable frequency oscillators and more particularly to dial assemblies for such oscillators. I

In certain applications of variable frequency oscillators it is required that the output frequency of the oscillator be varied at a specific rate. It may also be required that a certain band of frequencies be swept repetitively and automatically. It is, of course, highly desirable to have a calibrated dial on such an oscillator that it is synchronized with the sweeping apparatus which may be used to set the band of frequencies to be swept.

An object of this invention is to provide a dial assembly for a motor driven variable frequency oscillator that is synchronized with the sweeping apparatus and frequency calibrated.

Another object of this invention is to provide such a dial assembly which permits selected bands of frequencies to be automatically and repetitively swept.

A further object of this invention is to provide such a dial assembly which may be operated either manually or automatically.

Still a further object of this invention is to provide such a dial assembly which permits the band of frequencies to be swept to be easily varied.

Yet another object of this invention is to provide such a dial assembly that is simple and inexpensive to fabricate and assemble.

Other objects and advantages of this invention are apparent from the following description and accompanying drawings.

Reference is now made to the drawings wherein:

Fig. 1 is an exploded view of the dial assembly;

Fig. 2 is a side elevation of the dial assembly;

Fig. 3 is a simplified drawing showing the dial assembly as connected with the variable frequency oscillator tuning element;

Fig. 4 illustrates the unique construction of the limit stops; and

Fig. 5 is a schematic representation of a second embodiment of the invention.

Referring to one preferred embodiment of the invention illustrated in Fig. 1 it can be seen that the dial assembly advantageously comprises calibrated disc 1 and end disc 2 spaced apart by center disc 3. It will be noted that calibrated disc 1 and end disc 2 are of equal diameter, while center disc 3 is of somewhat smaller diameter. The three discs are secured as a unit by a cover 4 (Figure 2) to a flanged bushing 5 which is affixed to a shaft 6 advantageously by a set screw. The face of the calibrated disc 1 is frequency calibrated in accordance with the capacity of the oscillator.

It can be see that this construction in effect results in a single plate 7 with a groove 8 about its periphery (see Figure 2). Fitted in the groove 8 are two limit stops 9 strung on a thin wire 10 through holes 11 in the limit stops 9. Wire as used herein includes other similar members such as string, cord, etc., but wire of the piano wire type is used in the preferred embodiment.

The wire 10 and consequently the limit stops 9 are held in the groove by a spring or other resilient means 12 joined to each end of the wire 10. The spring 12 exerts sufficient tension on the wire 10 to prevent the limit stops 9 from sliding about the groove 8 of their own accord or when in contact with the switch 20 hereinafter described, but the tension thus exerted is not enough to prevent the limit stops 9 from being moved about the groove 8 either manually or by being urged against a center stop 22 also hereinafter described.

Figure 3 illustrates the dial assembly in conjunction with an oscillators tuning element, i. e., its frequency varying means 14. A first sheave 13 mounted on the shaft 6 is coupled by a belt 15 to a second sheave 16 which is mounted on an axle 17. The axle 17 extends through the second sheave 16 to a manual tuning knob 18 at one end, and through a magnetic coupling 26 to a motor or other drive means 19 at the other end.

While a magnetic coupling is preferred, a friction coupling or other coupling adapted to slip when the manual tuning knob is actuated during operation of the equipment, may be used Positioned above the plate 7 is a switch 20 having a leaf control 2.5. which is connected through appropriate circuitry to the motor or other drive means 19. The switch 2% is so constructed that the leaf 21 may move laterally in either direction. The switch 26 is connected to the drive means 1% in such relation that lateral movement of the leaf in either direction to the point of contact causes the drive means to reverse its direction of rotation.

It is apparent to those skilled in the art that while a leaf switch is preferred for economy and simplicity, other types of switching means might be used. In the embodiment illustrated, the switch 20 is contained in an appropriate housing and is held in such relation to the plate '7 that the limit stops 9 may make contact with the leaf 21. Just below the switch 20 is a center stop 22. The center stop 22 is placed in such relation to the plate 7 and the switch Ztl that the limit stops 9 make contact therewith in such manner to prevent the limit stops from riding over the leaf 21 after the switch is actuated or during careless manual handling of the equipment. This is accomplished by a channel 23 (see Figure 4) on the side of the limit stops 9 nearest the center stop 22. The channel 23 does not extend the full length of the limit stops 9 but terminates in a shoulder 24. This portion of the limit stops, the shoulder 24, is so spaced from the face 25 of the limit stops 9 as to contact the center stop 22 immediately after the face 25 has actuated the leaf switch 20.

When it is desired that a certain band of frequencies be swept, the maximum and minimum frequencies of the band are selected by the limit stops 9. This setting may be done manually by moving each of the stops 9 to the appropriate frequency indicia on the calibrated face of the plate '7. If desired the tuning knob 18 may be rotated thereby rotating the plate 7 and the limit stops 9. One of the limit stops 9 may be brought in turn into contact with the center stop 22 and the rotation of the plate 7 may be continued until the limit stop 9 is at the proper setting. Then the operation is repeated with respect to the other limit stop 9.

iVhen the appropriate frequencies have been thus se lected the motor and magnetic coupling are energized, causing the axle 17 to rotate. This movement is transmitted through belt 15 to the shaft 6 thereby rotating the tuning element and the plate 7. The rotation continues until one of the limit stops 9 contacts the leaf 21 thereby actuating the switch 2%) which causes the motor to reverse. The plate 7 and the tuning element 14 rotate in the reverse direction until the other limit stop 9 contacts the leaf 21 whereupon the cycle repeats and continues.

It can be seen that it is an easy operation to vary the band of frequencies even while the apparatus is sweeping. The limit stops 9 may be either moved. by hand or the knob 18 may be used as mentioned above. When the knob 18 is rotated while the motor is energized, it will be understood that the magnetic coupling 26 be tween the axle 17' and the motor is overridden.

Modifications can be made in the structures as de scribed above without departure from the scope of the invention.

For example, the principles of the structure heretofore described may be employed in an assembly of rectilinearly moving parts such as that illustrated schematically in Figure 5. There a drive means 29 operates through a pinion 30 and a rack 31 to move a yoke 32. The yoke 32 moves a calibrated dial 33 rectilinearly and also actuates the frequency varying means .34 with synchronous rectilinear motion. Two limit stops'itS are both carried on the dial33 and move in a path to engage and activate a switch 36. The switch 36 is connected to control the direction of drive from the drive means 29.

Accordingly, the foregoing description is to be construed as illustrative and not as a limitation upon the scope of the invention as defined in the following claims.

I claim:

1. In a variable frequency oscillator having frequency varying means and reversible drive means for actuating said frequency varying means to effect a sweeping of frequencies, a dial andcontrol assembly comprising a calibrated dial coupled to said frequency varying means so as to move synchronously wi h said frequency varying means; said dial being circular in shape andhaving a groove about its periphery; a wire with the ends there of joined by resilient means, said wire and resilient means being positioned in said groove; a first and second limit stop, bothshaped on one side thereof to conform to the periphery of said dial, each such stop being mounted with a portion thereof extending into said groove and having a hole therein through whichvsaid wire passes, whereby said stops are held on the periphery of said dial and are slidable with respect thereto; a switch connected to said drive means responsive to contact against either side there of to cause reversal of the direction of movement of said drive means and thereby the direction of movement of said dial and of said frequency varying means, said switch being positioned between and in the path of move ment of said limitstops so as to be responsive to either of said limit stops when it moves into juxtaposition with said switch.

2. The invention defined in claim 1 characterized by addition of a center-stop in juxtaposition with said switch and in thepath of movement of a portion of said limit stops, and wherein the portion of said limit stops which engage said center stop are disposed with respect to the portion of said limit stops which actuate said switch, so that the center stop isengaged whenever a limit stop passes the position at which it actuates said switch.

3. in a variable frequency oscillator having frequency varying means, the combination therewith of a reversible drive means for operating said frequency varying means to efiect a sweeping of frequencies, a dial connected to said reversible drive means for rotation in either direction in synchronism therewith, a pair of limit stops slidably carried on said dial for are ate movement rela tive thereto, yieldable means normally holding said limit stops in selected angularly spaced positions of said dial for movement therewith along an arcuate path, a switch disposed between said limit stops in said arcnate path, said switch being connected to said reversible drive means and being operative when engaged from one direction on said arcuate path to effect rotation of said reversible drive toward said one direction and when engaged from the opposite direction along said arcuate path to cause rotation of said reversible drive means toward said opposite direction, and stop means in said arcuate path to prevent further uni-directional movement or" a limit stop after operative engagement of said limit stop with said switch.

4. The invention defined in claim '3 characterized by the addition of a tuning knob coupled with said dial and said frequency varying means whereby manual rotation of said tuning knob effects rotation of said dial; and a coupling between said drive means and said dial which is adapted to slip when said manual tuning knob is 'operated. I

5. In a variable frequency oscillator having frequency varying means, the combination therewith of a reversible drive means for operating said frequency varying means to effect a sweeping of frequencies, a dial connected to said reversible drive means to rotate in opposite, directions in synchronism therewith, at least one limit stop slidably carried on said dial for arcuate movement relative thereto in said opposite directions, yieldable means normally holding said limit Stopon said dial for move ment therewith, a switch disposed in the path of move ment of said limit stop, said switch being connected with said reversible drive and being operative when engaged from either of said opposite directions to cause said reversible drive means to rotate, said dial toward said either direction, and stop means in the path of movement of said limit stop to preventfurtheruni-directional movement of said limit stop after operative engagement thereof with said switch. 7 V

6. in a'variable frequency oscillator having frequency varying means, the combination therewith of a reversible drive means for operating said, frequency varying means to effect a sweeping of frequencies, a dial connected to said reversible drive means to movein first and second opposite directions in synchronism therewith, a pair of limit stops slidably carried on said dial for movement relative thereto in said first and second opposite directions, yieldable 'rneans normally holding said limit stops in selectedispaced positions on said dial for movement therewith, a switch disposed between-said limit stops in the path-of,movement-thereof, said switch being connected with said reversible drive means and being operative whenengaged from one direction ,to cause said reversible drive means to move said dial in said first direction and when engaged from the opposite direction to cause said reversible drive means to move said dial in said second direction, and stop means in the path of movement of said limit stops ,to prevent further unidirectional'movement of a limit stop after operative engagement thereof with said switch.

References (Iited in the tile of this patent UNITED STATES PATENTS 2,422,180 Broadbent June 17, 1947 

